2,2-Dimethyl-1,3-dioxane-4,6-dione → 1,3-Dioxane-4,6-dione, 5-[[(6-methoxy-3-pyridinyl)amino]methylene]-2,2-dimethyl-

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Reaction Steps

A solution of 5-amino-2-methoxypyridine (50 g, 0.4 mol) in ethanol (300 ml) was treated with 2,2-dimethyl-[1,3]dioxane-4,6-dione (Meldrum's acid) (68 g) and triethylorthoformate (66 ml). The mixture was heated to reflux for 2 hours, then allowed to cool. Filtration afforded the intermediate 5-[(6-methoxy-pyridin-3-ylamino)-methylene]-2,2-dimethyl-[1,3]dioxane-4,6-dione as a white solid (101.2 g). A portion of this material (50 g) was added to boiling Dowtherm A (300 ml) over 3 minutes under a stream of argon. The mixture was refluxed for a further 5 minutes then allowed to cool before adding to ether. Filtration and drying afforded 6-methoxy-1H-[1,5]naphthyridin-4-one as a white solid (24.7 g, 70%).

Provenance & Evidence